The present invention relates to sealing devices and more particularly to seals, packings and wipers which are used to seal between two elements of an assembly which may be stationary or relatively moving.
It is common practice in the manufacture of composition packings or seals, both with and without a sealing lip(s), to construct the seal or packing from laminations or layers of suitable fabric materials superimposed upon one another and bonded together in a suitable fashion by means of thermosetting or thermoplastic resins. Typically, a fabric such as, for example, cotton, linen, nylon or the like, which is impregnated with a suitable resinous material, which can be either thermoplastic or thermosetting in nature, and the thus impregnated fabric is layered or laminated to the desired dimensions. The laminations are bonded together by means of pressure and temperature, the packing or seal being generally made into the desired configuration, e.g. with a sealing lip, at that time. U.S. Pat. No. 3,627,337 shows a laminated type packing comprised of alternating laminations of fibrous thermoplastic and fibrous thermosetting materials bonded together, molded and cured to the desired cross-sectional shape, the thermoplastic and thermosetting materials each being impregnated with a resinous compound which will mold to the desired shape and bond the laminations together.
It is also known in the manufacture of composition packings or seals to add particulate fillers to the impregnating compound used to bond the laminations together. Thus, fillers such as carbon black, graphite, clays, etc. are used to enhance the wear resistance, achieve lower friction, increase abrasion resistance, etc. The use of such particulate fillers does not always overcome the limitations imposed on the seal by the service conditions in which the packing or seal is placed because of the physical limitations inherent in the fabric used. Thus, for example, although a packing employing a cotton fabric and particulate carbon black as a filler may have higher heat resistance than a packing comprised of cotton alone, it may suffer from lower tensile strength.
Attempts have been made to construct composition packings or seals which will overcome some of the disadvantages discussed above in the use of particulate fillers. U.S. Pat. No. 3,879,044 to Estes discloses an O-ring construction in which a fluoroelastomeric sealant is combined with non-woven, radially oriented fibers, the fibers being disposed such that a least 25% form an angle of no more than 30.degree. from radii drawn through the center and through the plane of the sealant. The seal of the Estes patent is a substantially homogeneous seal in which the short fibers are dispersed, in oriented fashion, in the fluoroelastomeric sealants.
U.S. Pat. No. 3,873,168 to Viola et al discloses a laminated, annular article constructed from layers of woven glass and layers of woven graphite, the layers being impregnated with a suitable resin and bonded together to form the article. The article disclosed in the Viola et al patent, employing as it does woven graphite or woven carbon fibers, is relatively expensive to manufacture.
U.S. Pat. No. 3,901,517 to Heathcott discloses a dynamic seal which employs a relatively thin biasing section, and in which the biasing section of the seal may be comprised of a thermosetting or thermoplastic material reinforced with a fibrous material which can be in the form of a cloth or as a chopped or flocked filler.